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AL Electrician practice questions

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Question 1General Code Requirements, Definitions, and Wiring Design

Under the NEC, a conductor's ampacity is the maximum current it can carry continuously under the conditions of use without exceeding which limit?

  1. Its voltage rating
  2. Its temperature rating Correct answer.
  3. Its insulation resistance rating
  4. Its short-circuit withstand rating

Explanation

Article 100 defines ampacity as the maximum current, in amperes, that a conductor can carry continuously under the conditions of use without exceeding its temperature rating. The insulation and termination temperature ratings, together with the installed conditions, therefore set the current limit.

Question 2General Code Requirements, Definitions, and Wiring Design

A load is classified as continuous for NEC sizing purposes when it is expected to operate at maximum current for at least how long?

  1. 1 hour
  2. 30 minutes
  3. 3 hours Correct answer.
  4. 4 hours

Explanation

Article 100 defines a continuous load as one expected to operate at maximum current for three hours or more. That definition drives the 125 percent sizing factors applied to conductors, feeders and overcurrent devices.

Question 3General Code Requirements, Definitions, and Wiring Design

For equipment operating at 120/240 V, single phase, the minimum depth of clear working space in front of the equipment is:

  1. 1200 mm (4 ft)
  2. 900 mm (3 ft) Correct answer.
  3. 450 mm (18 in)
  4. 600 mm (24 in)

Explanation

Section 110.26(A)(1) sets working-space depth by voltage to ground and by the condition of the space. For equipment operating at not more than 150 V to ground, Condition 1 requires 900 mm (3 ft) of clear depth.

Question 4General Code Requirements, Definitions, and Wiring Design

The grounded conductor of a 120/240 V single-phase branch circuit must be identified by which finish or colour?

  1. Bare copper
  2. Black
  3. Green
  4. White or light gray Correct answer.

Explanation

Section 200.6 requires grounded conductors to be identified by a white or light gray finish, or by three continuous white stripes on certain cable assemblies. Green and bare finishes are reserved for equipment grounding conductors.

Question 5General Code Requirements, Definitions, and Wiring Design

When calculating box fill, a single receptacle or switch mounted on a yoke is counted as how many conductor volumes?

  1. Four conductor volumes
  2. Two conductor volumes Correct answer.
  3. Three conductor volumes
  4. One conductor volume

Explanation

Section 314.16(B)(4) counts each yoke or strap as two conductors based on the largest conductor in the box. This allows for the space occupied by the device body and its terminals.

Question 6General Code Requirements, Definitions, and Wiring Design

Under Article 100, an outlet is best described as:

  1. The point where the serving utility's conductors meet the premises wiring
  2. A contact device installed for the connection of an attachment plug
  3. Any enclosure where conductors are spliced together
  4. A point on the wiring system where current is taken to supply a load Correct answer.

Explanation

Article 100 defines an outlet as a point on the wiring system at which current is taken to supply utilization equipment. It is a point of use, not a box, not a device, and not the service point.

Question 7General Code Requirements, Definitions, and Wiring Design

An overcurrent protective device that opens the circuit by melting a metal link when current exceeds its rating is a:

  1. Circuit breaker
  2. Disconnecting means
  3. Fuse Correct answer.
  4. Contactor

Explanation

Article 100 defines a fuse as an overcurrent protective device with a circuit-opening fusible part that is heated and severed by the current passing through it. Breakers and contactors open by mechanical means.

Question 8General Code Requirements, Definitions, and Wiring Design

Which of the following is a standard ampere rating for fuses and inverse-time circuit breakers recognized by the NEC?

  1. 85 A
  2. 150 A Correct answer.
  3. 55 A
  4. 75 A

Explanation

Section 240.6(A) lists the standard ampere ratings, and 150 A appears on that list. Ratings such as 55 A, 75 A and 85 A are not standard and may be used only where the code specifically permits.

Question 9General Code Requirements, Definitions, and Wiring Design

A branch circuit supplies a 40 A continuous load and no other load. The overcurrent device protecting the circuit must have a rating of not less than:

  1. 50 A Correct answer.
  2. 40 A
  3. 45 A
  4. 60 A

Explanation

Section 210.20(A) requires the branch-circuit overcurrent device to be sized at not less than 125 percent of the continuous load plus 100 percent of the noncontinuous load. Here 40 A multiplied by 1.25 equals 50 A, which is also a standard rating.

Question 10General Code Requirements, Definitions, and Wiring Design

Four current-carrying conductors are installed in a single raceway. Under Table 310.15(C)(1), their ampacities must be adjusted to what percentage of the table value?

  1. 80 percent Correct answer.
  2. 70 percent
  3. 90 percent
  4. 100 percent

Explanation

Table 310.15(C)(1) requires an 80 percent adjustment where four to six current-carrying conductors are installed in a raceway or cable. Higher conductor counts require 70 percent or less.

Question 11General Code Requirements, Definitions, and Wiring Design

A 120 V branch circuit has a calculated voltage drop of 7.2 V. What is the percentage drop, and how does it compare with the NEC recommendation?

  1. 6 percent, which meets the recommended maximum for feeders and branch circuits combined
  2. 3 percent, which meets the recommendation
  3. 6 percent, which exceeds the recommended 3 percent for a branch circuit Correct answer.
  4. 5 percent, which exceeds the recommendation

Explanation

Dividing 7.2 V by 120 V gives a 6 percent drop. The informational notes to 210.19(A) recommend a maximum 3 percent drop on a branch circuit and 5 percent total for the feeder plus branch circuit, so this design exceeds both recommendations.

Question 12General Code Requirements, Definitions, and Wiring Design

In a dwelling unit, ground-fault circuit-interrupter protection is required for which of the following?

  1. A receptacle outlet in a bathroom Correct answer.
  2. A receptacle outlet in a bedroom
  3. A lighting outlet in a bathroom
  4. A receptacle outlet in a dining room

Explanation

Section 210.8(A)(1) requires GFCI protection for all receptacles in dwelling-unit bathrooms. Dining-room and bedroom receptacles fall under other rules, and a lighting outlet is not a receptacle outlet.

Question 13General Code Requirements, Definitions, and Wiring Design

Which protection is required for 125 V, 15 A and 20 A branch circuits supplying outlets in dwelling-unit bedrooms?

  1. Isolation monitoring
  2. Ground-fault circuit-interrupter protection
  3. Arc-fault circuit-interrupter protection Correct answer.
  4. Surge protective device

Explanation

Section 210.12(A) requires arc-fault circuit-interrupter protection for 125 V, 15 A and 20 A branch circuits supplying outlets in dwelling-unit bedrooms. GFCI protection addresses shock hazards and is a separate requirement.

Question 14General Code Requirements, Definitions, and Wiring Design

A 50 A branch circuit uses copper conductors in a raceway and terminates on equipment rated 75 degrees C. The minimum conductor size is:

  1. 8 AWG Correct answer.
  2. 6 AWG
  3. 10 AWG
  4. 4 AWG

Explanation

In the 75 degrees C column of Table 310.16, 8 AWG copper has an ampacity of 50 A. The conductor must have an ampacity not less than the branch-circuit rating after any correction or adjustment.

Question 15General Code Requirements, Definitions, and Wiring Design

The minimum width of the clear working space in front of electrical equipment must be the width of the equipment or:

  1. 600 mm (24 in), whichever is greater
  2. 1000 mm (40 in), whichever is greater
  3. 762 mm (30 in), whichever is greater Correct answer.
  4. 450 mm (18 in), whichever is greater

Explanation

Section 110.26(A)(2) requires the working space to be at least as wide as the equipment and never less than 762 mm (30 in). The width is measured along the equipment.

Question 16General Code Requirements, Definitions, and Wiring Design

In a dwelling-unit living room, no point along the floor line of any wall space may be more than what distance from a receptacle outlet?

  1. 600 mm (2 ft)
  2. 1.8 m (6 ft) Correct answer.
  3. 900 mm (3 ft)
  4. 1.5 m (5 ft)

Explanation

Section 210.52(A)(1) requires receptacles so that no point along the floor line of any wall space is more than 1.8 m (6 ft) from a receptacle. This general spacing rule keeps cords from being run long distances.

Question 17General Code Requirements, Definitions, and Wiring Design

Type NM cable must be secured within what distance of boxes and at what maximum intervals?

  1. 600 mm (24 in) of the box, then at intervals not exceeding 3.0 m (10 ft)
  2. 450 mm (18 in) of the box, then at intervals not exceeding 1.8 m (6 ft)
  3. 300 mm (12 in) of the box, then at intervals not exceeding 1.4 m (4.5 ft) Correct answer.
  4. 150 mm (6 in) of the box, then at intervals not exceeding 1.4 m (4.5 ft)

Explanation

Section 334.30 requires Type NM cable to be secured within 300 mm (12 in) of each box and at intervals not exceeding 1.4 m (4.5 ft). This keeps the cable from being strained or damaged.

Question 18General Code Requirements, Definitions, and Wiring Design

For a one-family dwelling, the general lighting load used in a feeder or service calculation is:

  1. 10 VA per square foot
  2. 5 VA per square foot
  3. 3 VA per square foot Correct answer.
  4. 1 VA per square foot

Explanation

Table 220.12 sets the general lighting load for a one-family dwelling at 33 VA per square metre, which is 3 VA per square foot. That figure is the starting point of the standard feeder and service calculation.

Question 19General Code Requirements, Definitions, and Wiring Design

Where is the main bonding jumper installed, and what does it connect?

  1. At every junction box, connecting the equipment grounding conductor to the box
  2. At the load end of the circuit, connecting the grounded circuit conductor to the utilization equipment enclosure
  3. In each panelboard, connecting the neutral bar to the metal enclosure
  4. At the service equipment, bonding the grounded conductor to the equipment grounding conductors Correct answer.

Explanation

Sections 250.24(B) and 250.28 require a main bonding jumper at the service equipment to connect the equipment grounding conductors to the grounded service conductor. This creates the single intentional connection that makes the grounding and bonding system effective.

Question 20General Code Requirements, Definitions, and Wiring Design

A box contains four 12 AWG conductors, one cable clamp, one receptacle mounted on a yoke, and one 12 AWG equipment grounding conductor. Using 2.25 cubic inches per 12 AWG conductor, the minimum box volume required is:

  1. 13.5 cubic inches
  2. 20.25 cubic inches
  3. 15.75 cubic inches
  4. 18.0 cubic inches Correct answer.

Explanation

Section 314.16(B) counts each 12 AWG conductor at 2.25 cubic inches. Four conductors total 9.0, the clamp counts as one conductor at 2.25, the yoke counts as two conductors at 4.5, and the equipment grounding conductor counts as one at 2.25, giving 18.0 cubic inches.

Question 21General Code Requirements, Definitions, and Wiring Design

A circuit is protected by a 60 A circuit breaker. The copper equipment grounding conductor run in the same raceway must be at least:

  1. 8 AWG
  2. 10 AWG Correct answer.
  3. 6 AWG
  4. 12 AWG

Explanation

Table 250.122 sizes the equipment grounding conductor according to the rating of the overcurrent device protecting the circuit. For a 60 A device, the minimum copper conductor is 10 AWG.

Question 22General Code Requirements, Definitions, and Wiring Design

In which case may the grounded conductor of a 3-phase, 4-wire wye circuit be left out of the current-carrying conductor count for ampacity adjustment?

  1. When it carries only the unbalanced current from line-to-neutral loads Correct answer.
  2. When it is bonded to the equipment enclosure at both the source and the load end
  3. When the circuit is protected by a ground-fault circuit interrupter
  4. When it has been sized larger than the ungrounded circuit conductors

Explanation

Section 310.15(E) allows the neutral of a 3-phase, 4-wire wye circuit to be omitted from the count when it carries only the unbalanced current from line-to-neutral loads. Where the neutral carries triplen harmonic current, it must be counted.

Question 23General Code Requirements, Definitions, and Wiring Design

Using the standard method for a one-family dwelling, the portion of the general lighting load between 3,001 VA and 120,000 VA may be taken at what demand factor?

  1. 40 percent
  2. 35 percent Correct answer.
  3. 30 percent
  4. 25 percent

Explanation

Table 220.42 applies 100 percent demand to the first 3,000 VA of the dwelling general lighting load and 35 percent to the remainder up to 120,000 VA. This demand factor reduces the calculated service and feeder load.

Question 24General Code Requirements, Definitions, and Wiring Design

The ampacity adjustment factors of Table 310.15(C)(1) need not be applied to conductors in a raceway or nipple where the length does not exceed:

  1. 450 mm (18 in)
  2. 600 mm (24 in) Correct answer.
  3. 300 mm (12 in)
  4. 150 mm (6 in)

Explanation

The exception to Table 310.15(C)(1) permits bundled conductors in a raceway or nipple not exceeding 600 mm (24 in) in length to be used without ampacity adjustment, provided the 30 percent fill limit of Chapter 9, Table 1 is met.

Question 25General Code Requirements, Definitions, and Wiring Design

A feeder supplies a 55 A continuous load and no other load. After applying the 125 percent factor, the minimum standard rating of the overcurrent device protecting the feeder is:

  1. 80 A
  2. 100 A
  3. 70 A Correct answer.
  4. 60 A

Explanation

Section 215.3 requires feeder overcurrent devices to be sized at not less than 125 percent of the continuous load, giving 55 A multiplied by 1.25, or 68.75 A. The next standard rating in 240.6(A) that is not less than this value is 70 A.

Question 26General Code Requirements, Definitions, and Wiring Design

Under Article 100, a continuous load is a load in which the maximum current is expected to continue for:

  1. 3 hours or more Correct answer.
  2. 1 hour or more
  3. 30 minutes or more
  4. 2 continuous hours or more

Explanation

Article 100 defines a continuous load as one where the maximum current is expected to continue for 3 hours or more. That threshold drives the 125 percent sizing rules applied to branch-circuit conductors, overcurrent devices, and feeders in Articles 210 and 215.

Question 27General Code Requirements, Definitions, and Wiring Design

For equipment to be considered readily accessible, it must be capable of being reached quickly for operation, renewal, or inspection without:

  1. using a portable ladder or a lift
  2. opening a locked door with a key
  3. climbing over or removing obstacles Correct answer.
  4. arranging a scheduled outage with the utility

Explanation

The Article 100 definition of readily accessible requires that the item can be reached quickly without climbing over or removing obstacles and without portable ladders. The concept addresses the physical effort and delay of access, not administrative controls such as locks or utility coordination.

Question 28General Code Requirements, Definitions, and Wiring Design

The minimum number of 20-ampere small-appliance branch circuits that must be provided for the kitchen and dining areas of a one-family dwelling is:

  1. two Correct answer.
  2. four
  3. one
  4. three

Explanation

Section 210.11(C)(1) requires at least two 20-ampere small-appliance branch circuits to serve receptacle outlets in the kitchen, dining room, pantry, breakfast room, and similar areas. These circuits may also supply other specified outlets but must not serve lighting outlets.

Question 29General Code Requirements, Definitions, and Wiring Design

In a dwelling unit, which of these receptacle outlets must be listed as tamper resistant?

  1. Only receptacles installed outdoors
  2. All 125-volt, 15- and 20-ampere receptacles Correct answer.
  3. Only receptacles rated 20 amperes
  4. Only receptacles installed in kitchens and bathrooms

Explanation

Section 406.12 requires tamper-resistant receptacles for all 125-volt, 15- and 20-ampere receptacle outlets in dwelling units, with a limited list of exceptions such as those captured by a dedicated appliance. The requirement is not limited to any one room or to one ampere rating.

Question 30General Code Requirements, Definitions, and Wiring Design

Equipment intended to interrupt current at fault levels must have an interrupting rating not less than which value at its supply terminals?

  1. Ampacity of the supply conductors
  2. Rating of the next upstream overcurrent device
  3. Nominal system voltage
  4. Available short-circuit current Correct answer.

Explanation

Section 110.9 requires that equipment intended to break current at fault levels have an interrupting rating at nominal circuit voltage not less than the current that is available at the equipment's supply terminals. This is calculated available fault current, which is normally higher than the rating of any single upstream device.

Question 31General Code Requirements, Definitions, and Wiring Design

Except where a specific permission applies, the overcurrent protection for a 14 AWG copper branch-circuit conductor must not exceed:

  1. 15 amperes Correct answer.
  2. 10 amperes
  3. 20 amperes
  4. 25 amperes

Explanation

Section 240.4(D)(3) limits 14 AWG copper conductors to 15-ampere overcurrent protection unless one of the specific permissions in 240.4(E) or (G) applies, such as certain motor circuit applications. The rule protects small conductors whose ampacity is below the rating of the next standard device size.

Question 32General Code Requirements, Definitions, and Wiring Design

In a dwelling-unit kitchen, receptacle outlets along the wall countertop must be arranged so that no point along the wall line is more than what distance from a receptacle outlet?

  1. 24 inches Correct answer.
  2. 36 inches
  3. 12 inches
  4. 18 inches

Explanation

Section 210.52(C)(1) requires receptacle outlets along countertop wall spaces to be spaced so that no point along the wall line is more than 24 inches measured horizontally from a receptacle outlet. Receptacles must also be installed no more than 20 inches above the countertop surface.

Question 33General Code Requirements, Definitions, and Wiring Design

At an outlet where no equipment grounding conductor exists, a nongrounding receptacle may be replaced with a grounding-type receptacle if:

  1. the receptacle is mounted in a listed metal box
  2. the branch circuit is protected by a 20-ampere breaker
  3. a separate No. 12 AWG conductor is used for the neutral
  4. it is provided with ground-fault circuit-interrupter protection Correct answer.

Explanation

Section 406.4(D)(2) allows a grounding-type receptacle to replace a nongrounding receptacle where the receptacle is supplied by a ground-fault circuit interrupter, and it must be marked 'GFCI Protected' and 'No Equipment Ground.' This provides shock protection in the absence of an equipment grounding conductor.

Question 34General Code Requirements, Definitions, and Wiring Design

Unless a specific exception applies, a wall-mounted general-use snap switch must be installed so that its center is no more than what height above the floor?

  1. 6 ft 0 in
  2. 7 ft 6 in
  3. 6 ft 7 in Correct answer.
  4. 5 ft 9 in

Explanation

Section 404.8(A) requires switches and circuit breakers used as switches to be located so their center is not more than 6 ft 7 in above the floor or working platform. The rule keeps switching devices operable by ordinary persons without portable means.

Question 35General Code Requirements, Definitions, and Wiring Design

A rod-type grounding electrode that is not listed must be at least which length and diameter?

  1. 6 ft long and 3/4 in diameter
  2. 10 ft long and 5/8 in diameter
  3. 8 ft long and 3/4 in diameter
  4. 8 ft long and 1/2 in diameter Correct answer.

Explanation

Section 250.52(A)(5) requires rod and pipe electrodes to be at least 8 ft in length, and rods must be at least 1/2 in in diameter unless listed. Listed rods are permitted at 5/8 in diameter, and pipe or conduit electrodes must be at least trade size 3/4.

Question 36General Code Requirements, Definitions, and Wiring Design

A 120-volt, 20-ampere residential branch circuit protected by a GFCI is buried directly in earth as Type UF cable. The minimum cover required is:

  1. 24 inches
  2. 18 inches Correct answer.
  3. 12 inches
  4. 6 inches

Explanation

Table 300.5 permits 18 inches of cover for residential 120-volt branch circuits rated 20 amperes or less that are GFCI protected. Without that specific condition, direct-buried cables and conductors generally require 24 inches of cover.

Question 37General Code Requirements, Definitions, and Wiring Design

Three 1/0 AWG copper conductors with 75 degrees C insulation are installed in a raceway with no ampacity adjustment required. Their allowable ampacity from Table 310.16 is:

  1. 100 amperes
  2. 120 amperes
  3. 150 amperes Correct answer.
  4. 130 amperes

Explanation

Table 310.16 lists 1/0 AWG copper at 150 amperes in the 75 degrees C column. Because only three current-carrying conductors are present, no adjustment factor from Table 310.15(C)(1) applies.

Question 38General Code Requirements, Definitions, and Wiring Design

An 8 AWG THHN copper conductor with 90 degrees C insulation terminates on a circuit breaker marked 60/75 degrees C. What ampacity applies when sizing the conductor?

  1. 40 amperes
  2. 55 amperes
  3. 50 amperes Correct answer.
  4. 45 amperes

Explanation

Section 110.14(C) limits conductor ampacity to the temperature rating of the termination. Because the breaker is marked 60/75 degrees C, the 75 degrees C column applies, where 8 AWG copper is rated 50 amperes; the 90 degrees C insulation rating may not be used to exceed the termination rating.

Question 39General Code Requirements, Definitions, and Wiring Design

A service is supplied by 2/0 AWG copper service-entrance conductors. Using Table 250.66, the minimum copper grounding electrode conductor is:

  1. 6 AWG
  2. 4 AWG Correct answer.
  3. 1/0 AWG
  4. 2 AWG

Explanation

Table 250.66 sizes the grounding electrode conductor from the largest ungrounded service conductor. A 2/0 AWG copper service conductor falls in the row covering 2/0 through 3/0, which requires a 4 AWG copper grounding electrode conductor.

Question 40General Code Requirements, Definitions, and Wiring Design

Using Column C of Table 220.55, the demand load for a single 12 kW electric range in a dwelling unit is:

  1. 10 kW
  2. 6 kW
  3. 12 kW
  4. 8 kW Correct answer.

Explanation

Column C of Table 220.55 assigns a demand of 8 kW to a single household range rated 12 kW. The table recognizes that range demand does not increase proportionally with nameplate rating, so the calculated load is less than the connected load.

Question 41Wiring Methods, Materials, and Installation Practices

Type NM cable must be secured within what distance of a box and at what maximum interval along the run?

  1. Within 12 in of the box and at intervals not exceeding 3 ft
  2. Within 8 in of the box and at intervals not exceeding 6 ft
  3. Within 12 in of the box and at intervals not exceeding 4 1/2 ft Correct answer.
  4. Within 6 in of the box and at intervals not exceeding 4 1/2 ft

Explanation

Section 334.30 requires Type NM cable to be secured and supported within 12 in of each box and at intervals not exceeding 4 1/2 ft throughout the run. The securing means must be listed for the cable and must not damage the sheath. Where the cable enters a box through a raceway or cable fitting, the 12 in measurement is taken from the fitting.

Question 42Wiring Methods, Materials, and Installation Practices

In a box-fill calculation, a single yoke or strap that supports a receptacle counts as how many conductor volumes?

  1. Four conductors
  2. One conductor
  3. Three conductors
  4. Two conductors Correct answer.

Explanation

Section 314.16(B)(4) states that each yoke or strap containing one or more devices counts as two conductors based on the largest conductor present in the box. The volume is therefore two times the cubic-inch value for that conductor size. Cable clamps and connectors are counted separately as a single volume.

Question 43Wiring Methods, Materials, and Installation Practices

What is the minimum width of the working space required in front of a 24-inch-wide panelboard installed indoors?

  1. 24 inches
  2. 36 inches
  3. 30 inches Correct answer.
  4. 18 inches

Explanation

Section 110.26(A)(2) requires the working space in front of electrical equipment to be at least 30 in wide, or the width of the equipment if that is greater. Because this panelboard is only 24 in wide, the 30 in minimum governs. The space must be clear from the floor to the required height and extend the full depth of the working space.

Question 44Wiring Methods, Materials, and Installation Practices

In a dwelling unit, general wall receptacles must be installed so that no point along the floor line is more than what distance from a receptacle outlet?

  1. 6 ft Correct answer.
  2. 5 ft
  3. 8 ft
  4. 4 ft

Explanation

Section 210.52(A)(1) requires receptacle outlets along general walls so that no point on the floor line is more than 6 ft from one. This spacing rule is measured along the wall line, including around corners and into wall spaces 2 ft or wider. Fixed room dividers and sliding panels also affect where the measurement starts and stops.

Question 45Wiring Methods, Materials, and Installation Practices

Electrical metallic tubing must be secured within what distance of a box and at what maximum interval along the run?

  1. Within 3 ft of the box and at intervals not exceeding 10 ft Correct answer.
  2. Within 3 ft of the box and at intervals not exceeding 6 ft
  3. Within 12 in of the box and at intervals not exceeding 5 ft
  4. Within 18 in of the box and at intervals not exceeding 10 ft

Explanation

Section 358.30 requires EMT to be securely fastened within 3 ft of each box or termination and at intervals not exceeding 10 ft. Where structural members do not provide support, other approved means are permitted. The 3 ft dimension also applies to the first support on each side of a box.

Question 46Wiring Methods, Materials, and Installation Practices

Splices and taps of conductors in a raceway system are permitted in which location?

  1. Anywhere along the run if a listed splice connector is used
  2. Inside the raceway if the splice connector is listed for the location
  3. Only at panelboards and switchboards
  4. Only in a box, conduit body, or other enclosure provided with a cover Correct answer.

Explanation

Section 300.15 requires splices, taps, and terminations to be made only in boxes, conduit bodies, or other enclosures that are accessible and provided with covers. The purpose is to keep joints accessible and protected. A conduit body used for splices must be sized for the fill, and the cover must remain accessible.

Question 47Wiring Methods, Materials, and Installation Practices

A 240-volt branch-circuit cable direct buried beneath a residential lawn must have a minimum earth cover of what depth?

  1. 30 in
  2. 24 in Correct answer.
  3. 18 in
  4. 12 in

Explanation

Table 300.5 requires 24 in of cover for direct-buried conductors and cables operating at 0 to 1000 V where the reduced residential depth does not apply. The 12 in reduction is limited to residential branch circuits of 120 V or less, GFCI protected, and protected at 20 A or less. The cover is measured from the top of the buried cable to the finished grade.

Question 48Wiring Methods, Materials, and Installation Practices

Type NM cable is permitted in which of these installations?

  1. Inside the return-air plenum of a commercial building
  2. Buried directly in the earth beneath a driveway
  3. Encased in poured concrete
  4. Through bored holes in the wood studs of a dwelling wall Correct answer.

Explanation

Section 334.10 permits Type NM cable in one- and two-family dwellings and similar structures, including concealed within wood-frame walls and ceilings. Section 334.12 prohibits its use in wet locations, in plenum spaces, in masonry or concrete, and where exposed to corrosive conditions. Running through bored stud holes is a standard permitted use.

Question 49Wiring Methods, Materials, and Installation Practices

A box is marked with a volume of 30 cubic inches and contains four 12 AWG conductors, one cable clamp, and one duplex receptacle. Using Table 314.16(B) values, how much box volume does the fill consume?

  1. 18.0 cubic inches
  2. 13.5 cubic inches
  3. 11.25 cubic inches
  4. 15.75 cubic inches Correct answer.

Explanation

Each 12 AWG conductor counts 2.25 cubic inches, so four conductors take 9.0 cubic inches. The clamp counts as one 2.25 cubic inch volume, and the duplex receptacle yoke counts as two conductors, or 4.5 cubic inches. The total is 9.0 + 2.25 + 4.5 = 15.75 cubic inches, which is within the 30 cubic inch box.

Question 50Wiring Methods, Materials, and Installation Practices

A feeder is protected by a 60-ampere overcurrent device. What is the minimum size copper equipment grounding conductor required to be run with the feeder?

  1. 8 AWG
  2. 14 AWG
  3. 12 AWG
  4. 10 AWG Correct answer.

Explanation

Table 250.122 sizes the equipment grounding conductor by the rating of the overcurrent device protecting the circuit. For a 60 A device, the table requires 10 AWG copper. The conductor must be increased proportionally if the ungrounded circuit conductors are increased in size for voltage drop.